The present invention relates to a copying machine provided with a reciprocally movable original holder possessing an openable original cover.
In such a movable original holder type copying machine, as shown in Unexamined Patent Publications of No. 164352/1982 and No. 138662/1983, it has been already known to provide a locking mechanism for restricting movement of an original holder and a releasing mechanism for releasing the locking mechanism for the purpose of eliminating the unnecessary movement of the original holder as well as ensuring a reciprocation of the original holder to be stopped.
As shown in Unexamined Patent Pablications of No. 78849/1982 and No. 173733/1984, the copying machine has been known which is equipped with an original size detector for detecting automatically the size of an original placed on an original holder prior to the commencement of a copying operation. Such an original size detector performs the detection of original size from an ON-OFF detection signal issued by a switch which is turned on and off in accordance with the movement of an original cover for covering the original holder. If such an original size detector is applied to the afore-mentioned movable original holder type copying machine, there will be the following likelihood. When the switch actuatable in accordance with movement of the original cover is provided on the movable original holder, it becomes necessary to provide an electric wire for leading an detection signal from the movable original holder to the main body of an copying machine and consequently there arises the worry of breaking of the electric wire due to the movement of the original holder. Furthermore, when a switch actuatable in accordance with the movement of the original cover is provided in the main body of the copying machine in order to eliminate the aforementioned electric wire for detection, it is necessary to provide a lever for cooperatably connecting the original holder and the original cover so as to cause the switch to actuate in accordance with the original cover, which causes the lever to project from the original holder. Consequently, it becomes to provide a mechanism for drawing in the lever before the copying operation so that the lever may not incur any hindrance when the original holder moves at the copying operation, resulting in more complicated construction.
Since a detecting means for detecting the size of original comprising a light emission component and a light receiving component is usually provided in the main body of a copying machine, an accurate detection of the size of original is requires a fixed position of the original holder with respect to the main body of the copying machine. For this reason, in order to stop the original holder at a fixed position, a locking mechanism for restricting the movement of the original holder becomes necessary.
Besides this, in the case where the main body of a copying machine is divided into an upper unit and a lower unit, the upper unit being able to be rotated so as to perform maintenance inspection or jamming treatment, it is particularly necessary to provide such a locking mechanism for locking the original holder as mentioned above to prevent a shock from giving to the original holder and the main body due to the fact that when the upper unit is opened, the original holder moves rapidly in an inclined direction.
However, in a copying machine eqipped with the afore-mentioned locking mechanism, there is the following trouble. When an operator opens the upper unit to remove a sheet of jammed paper or a moving force is applied to the original holder, the lock mechanism comes into work. Even if the lock is released so that the original holder may move at the copying operation, the releasing will become troublesome. In particular, in a movable original holder type copying machine whose original holder is comparatively larger, releasing of the locking from the workable state gives the releasing mechanism a large burden.